A rapidly spreading intruder

A rapidly spreading intruder

Allen J. Schaben / Los Angeles Times

A Sahara mustard plant looms over nearby native wildflowers in Anza-Borrego Desert State Park. Sahara mustard made its way to the American Southwest with imported date palms in the 1920s. Since then, it has spread from Central California to Texas and from Colorado to Mexico.

A Sahara mustard plant looms over nearby native wildflowers in Anza-Borrego Desert State Park. Sahara mustard made its way to the American Southwest with imported date palms in the 1920s. Since then, it has spread from Central California to Texas and from Colorado to Mexico. (Allen J. Schaben / Los Angeles Times)

A Sahara mustard plant looms over nearby native wildflowers in Anza-Borrego Desert State Park. Sahara mustard made its way to the American Southwest with imported date palms in the 1920s. Since then, it has spread from Central California to Texas and from Colorado to Mexico.